Spinal disorders such as degenerative disc disease, disc herniation, osteoporosis, spondylolisthesis, stenosis, scoliosis and other curvature abnormalities, kyphosis, tumor, and fracture may result from factors including trauma, disease and degenerative conditions caused by injury and aging. Spinal disorders typically result in symptoms including pain, nerve damage, and partial or complete loss of mobility.
Non-surgical treatments, such as medication, rehabilitation and exercise can be effective, however, may fail to relieve the symptoms associated with these disorders. Surgical treatment of these spinal disorders includes discectomy, laminectomy, fusion and implantable prosthetics. As part of these surgical treatments, spinal implants are used. These implants must be made from biocompatible material having high tensile strength and various degrees of flexibility. One suitable material that can be used to produce these implants is thermoplastic composite material manufactured using a pultrusion process.
The pultrusion process as commonly practiced uses reinforcing material, for example, glass filaments, or other reinforcing fibers such as carbon and high strength organic fibers, combined in associated groupings or “tows” that are passed through a tank containing the polymer which is to form the continuous phase in the form of a liquid solution, or in melted form. The plastic coated tows are thereafter drawn through a heated die. The coated tows emerging from the heated die as a relatively rigid composite having reinforced fibers positioned throughout the material. In order to be able to pull the composite through the heated curing die there must be a relatively high percentage of reinforcing fibers in the composite. However, a composite material produced having a relatively high percentage of continuous reinforcing fibers results in a less flexible composite material than materials having a lower concentration of continuous fibers.
Accordingly, the thermoplastic composite material produced by existing pultrusion processes are often too rigid to be suitable for the manufacture of biological implants, for example spinal implants, because of the high percentage of continuous fibers required to support the existing pultrusion process make the material very rigid. This disclosure describes an improved pultrusion process and articles manufactured therefrom that has a lower fiber content and is more flexible than existing pultrusion products.